Multi-carrier communication apparatus

ABSTRACT

In a multi-carrier communication apparatus, it is an object of the invention to increase the amount of data per unit time greatly with the band width kept unchanged. A modulator ( 102 ) sequentially performs primary modulation of data ( 101 ) which are first transmitted data on the basis of, for example, QPSK modulation. A pattern generating unit ( 104 ) generates a pattern of particular signals which is to be allocated to sub-carriers of a matrix formed by arranging a plurality of sub-carriers arranged in the direction of a frequency axis into a plurality of symbols in the direction of a time axis. The pattern is determined based on data ( 103 ) which are second transmitted data. A mapping unit ( 105 ) allocates the sub-carriers modulated by the data ( 101 ) at the modulator ( 102 ) and the pattern of the particular signals to the sub-carriers of the matrix.

TECHNICAL FIELD

The present invention relates to a multi-carrier communication apparatuswhich performs communication using a plurality of sub-carriers.

BACKGROUND ART

Recently, in accordance with the advance of broad band communications,expectations for radio communication apparatus capable of instantaneousand stable transmission of a large amount of data and the development ofsuch apparatus are increased. In particular, multi-carrier transmissionsystems for transmitting data using a plurality of sub-carriers arerecently in the focus of attention for their excellent featuresincluding capability of reducing interferences of delayed waves inmultiple paths, the feature originating in the use of a plurality ofsub-carriers which allows symbols to be transmitted at a low rate byeach sub-carrier.

Orthogonal frequency division multiplexing (OFDM) is a type ofmulti-carrier transmission systems. The orthogonal frequency divisionmultiplexing has system in which all sub-carriers are orthogonal to eachother and adjoining sub-carriers are overlapped. The orthogonalfrequency division multiplexing is adopted and is being put in practicaluse in terrestrial digital broadcasts and WLANs of a 5 GHz band (IEEE802.11a) for its extremely high spectral efficiency.

Multi-carrier transmission according to the related art will now bedescribed.

FIG. 5 shows an example of a configuration of a transmission apparatusaccording to the related art utilizing orthogonal frequency divisionmultiplexing that is a type of multi-carrier transmission.

In the transmission apparatus according to the related art shown in FIG.5, data 501 to be transmitted are subjected to primary modulation by amodulator 502 which utilizes, for example, the QPSK modulation method. Acomplex signal obtained by the primary modulation at the modulator 502is subjected to serial-to-parallel conversion by a serial-to-parallelconverter 503, then, rearranged according to the arrangement ofsub-carries in the direction of a frequency axis, and thereaftersubjected to inverse Fourier transformation by an IFFT 504. The datawhich have been subjected to inverse Fourier transformation areconverted into complex data in the direction of a time axis by aparallel-to-serial converter 505 which performs parallel-to-serialconversion. A GI adding unit 506 adds a guard interval GI for avoidinginterferences between symbols attributable to delayed waves to the datawhich are thereafter put on a carrier wave by an orthogonal modulator507 and are transmitted by a transmitter 508.

As thus described, complex data in the direction of a time axis whichhave been subjected to inverse Fourier transformation by the IFFT 504and added with a guard interval GI constitutes one OFDM symbol, andsubsequent OFDM symbols are sequentially repeated in units depending onthe size of the inverse Fourier transformation.

FIG. 6 shows an example of a configuration of a reception apparatusaccording to the related art utilizing orthogonal frequency divisionmultiplexing that is a type of multi-carrier transmission.

In the reception apparatus according to the related art shown in FIG. 6,signals received by a receiver 601 are converted into in-phasecomponents I and orthogonal components Q by an orthogonal demodulator602. Thereafter, synchronization of the OFDM symbols is established, andguard intervals GI which are unnecessary for demodulation are removed bya GI removing unit 603. The complex signals from which guard intervalsGI are removed are subjected to serial-to-parallel conversion by an S/P604. Thereafter, the complex signals are converted into complex signalsassociated with sub-carriers in the direction of a frequency axis by anFFT 605 which performs Fourier transformation. Finally, the complexsignals associated with the arrangement of sub-carriers in the directionof the frequency axis are subjected to parallel-to-serial conversion bya P/S 606. The signals are then QPSK-demodulated by, for example, ademodulator 607 to obtain data 608 which are received data.

The use of Fourier transformation in generating orthogonal multiplecarriers in such a manner is most characteristic of orthogonal frequencydivision multiplexing. In normal orthogonal frequency divisionmultiplexing, for example, data to be transmitted in time series whichhave are modulated by allocating them to sub-carriers which haverespective frequencies f1 to f8 and which are orthogonal to each otheras shown in FIG. 7 to be described later. This process will be describedwith reference to FIG. 7.

FIG. 7 is a diagram for explaining a relationship between data andsub-carriers in a multi-carrier communication apparatus according to therelated art.

As shown in FIG. 7, data D1 to D8 to be modulated that are input in timesequence are simply allocated to sub-carriers having respectivefrequencies f1 to f8 and are subjected to inverse Fourier transformationto generate one OFDM symbol.

For example, techniques for increasing the amount of data that can betransmitted using one OFDM symbol include proposals in which first dataare allocated to a combination itself of ten sub-carriers selected fromamong sixteen sub-carriers and in which second data are allocated toeach of the selected ten sub-carriers, the proposal being aimed atincreasing the amount of data that can be transmitted and reducing apeak-to-average power ratio PAPR of the transmitted wave through aresultant reduction in the number of sub-carriers (see Patent Document1, for example). This technique makes it possible to improve the powerefficiency of a power amplifier that forms a part of a radio unitbecause it allows a reduction in the number of sub-carriers when theamount of data to be transmitted is unchanged and allows thepeak-to-average power ratio PAPR of the transmitted wave to be improved.

Patent Document 1: JP-A-2001-148678

In the multi-carrier communication apparatus disclosed in PatentDocument 1, however, since first data are allocated to the pattern of acombination of an arbitrary number of sub-carriers selected from amongsub-carriers arranged in the direction of a frequency axis, the amountof the first data can be increased only to a maximum that is within therange of the number of sub-carriers in the direction of the frequencyaxis. Therefore, a limit has existed for the increase in the amount ofdata that can be transmitted using one OFDM symbol.

For example, ₈C₇=8=2³ combinations (C represents combination) areavailable for selection of seven sub-carriers from among eightsub-carriers, and three bits of data can therefore be transmitted asfirst data. With the multi-carrier communication apparatus disclosed inPatent Document 1, the amount of data transmitted can be increased byonly three bits when compared to that achievable with generalmulti-carrier transmission systems in which data are transmitted byallocating them only to each of the eight sub-carriers.

The invention is made taking the above-described situation intoconsideration, and it is an object of the invention to provide amulti-carrier communication apparatus capable of greatly increasing theamount of data transmitted or received per unit time with the frequencyband width kept unchanged.

DISCLOSURE OF THE INVENTION

A multi-carrier communication apparatus according to the invention is amulti-carrier communication apparatus for transmitting data using aplurality of sub-carriers, comprising a determining unit whichdetermines a pattern of particular signals associated with first data,an allocating unit which allocates the determined pattern tosub-carriers of a matrix that is formed by arranging a plurality ofsub-carriers arranged in the direction of a frequency axis in thedirection of a time axis, an allocating unit which allocatessub-carriers modulated by second data to the part of the matrix otherthan the particular signals, and a transmitting unit which transmits theparticular signals allocated to the matrix and the sub-carriersmodulated by the second data.

With this configuration, the first data associated with the pattern ofthe particular signals allocated to the sub-carriers of the matrix andthe second data that are the modulated sub-carriers allocated to thepart of the matrix other than the particular signals are transmitted toa receiving end.

The amount of the first data which can be transmitted within a time thatis determined by the number of symbols in the direction of the time axisof the matrix is determined by the number of patterns of the particularsignals. The number of the patterns is the number of combinationsavailable for selection of an arbitrary number of elements from amongthe matrix, and the number of the combinations greatly increasesdepending on the size of the matrix.

Therefore, the amount of the first data that can be transmitted can begreatly increased by increasing the number of the sub-carriers in thedirection of the frequency axis and the number of the symbols in thedirection of the time axis of the matrix. It is thus possible totransmit a great volume of data. Therefore, the amount of datatransmitted per one symbol time consequently increases, which allows anincrease in the amount of data transmitted per unit time.

A multi-carrier communication apparatus according to the inventioncomprises a detecting unit which detects a pattern of particular signalsassociated with first data which are allocated to sub-carriers of amatrix formed by arranging a plurality of sub-carriers arranged in thedirection of a frequency axis obtained from received data in thedirection of a time axis, a restoring unit which restores the first dataassociated with the detected pattern, and a demodulating unit whichdemodulates second data from sub-carriers which have been modulated bythe second data that are allocated to the part of the matrix other thanthe particular signals.

This configuration allows reception of the first data associated withthe pattern of the particular signals allocated to the sub-carriers ofthe matrix and the second data that are the modulated sub-carriersallocated to the part of the matrix other than the particular signals.

The amount of the first data which can be transmitted within a time thatis determined by the number of symbols in the direction of the time axisof the matrix is determined by the number of patterns of the particularsignals. The number of the patterns is the number of combinationsavailable for selection of an arbitrary number of elements from amongthe matrix, and the number of the combinations greatly increasesdepending on the size of the matrix. Therefore, the amount of the firstdata that can be received greatly increases accordingly.

Thus, the amount of the first data that can be received greatlyincreases, the greater the number of the sub-carriers in the directionof the frequency axis and the number of the symbols in the direction ofthe time axis of the matrix. It is thus possible to receive a greatvolume of data. Therefore, the amount of data received per one symboltime consequently increases, which allows an increase in the amount ofdata received per unit time.

In a multi-carrier communication apparatus according to the invention,each of the plurality of sub-carriers arranged in the direction of thefrequency axis has an orthogonal relationship with a sub-carrieradjacent thereto.

In this configuration, since no interference occurs even though thesub-carriers are arranged adjacent to each other, the number ofsub-carriers can be increased by reducing the intervals at which thesub-carriers are arranged, which makes it possible to increase theamount of data communicated with the frequency band width keptunchanged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic configuration of a multi-carrier communicationapparatus for explaining a first embodiment of the invention;

FIG. 2 shows a matrix formed by a plurality of sub-carriers arranged inthe direction of a frequency axis and a plurality of OFDM symbolsarranged in the direction of a time axis in the multi-carriercommunication apparatus for explaining the first embodiment of theinvention;

FIG. 3 shows waveforms of sub-carriers associated with respectiveelements of the matrix of a plurality of sub-carriers arranged in thedirection of the frequency axis and a plurality of OFDM symbols arrangedin the direction of the time axis in the multi-carrier communicationapparatus for explaining the first embodiment of the invention;

FIG. 4 shows a schematic configuration of a multi-carrier communicationapparatus for explaining a second embodiment of the invention;

FIG. 5 shows an example of a configuration of a transmission apparatusaccording to the related art utilizing orthogonal frequency divisionmultiplexing that is a type of multi-carrier transmission;

FIG. 6 shows an example of a reception apparatus according to therelated art utilizing orthogonal frequency division multiplexing that isa type of multi-carrier transmission; and

FIG. 7 is a diagram for explaining a relationship between data andsub-carriers in a multi-carrier communication apparatus according to therelated art.

Reference numerals 101, 102, 103, 104, 105, 106, 107, 108, and 110 inthe figures represent an item of data (first transmitted data), amodulator, another item of data (second transmitted data), a patterndetermination unit, a mapping unit, an IFFT, a P/S, a GI adding unit,and a transmission unit, respectively.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the invention will now be described with reference to thedrawings.

FIRST EMBODIMENT

FIG. 1 shows a schematic configuration of a multi-carrier communicationapparatus for explaining a first embodiment of the invention.

The multi-carrier communication apparatus includes a modulator 102, apattern determination unit 104 for determining a pattern of particularsignals to be described later, a mapping unit for allocating signals, anIFFT 106 for performing inverse Fourier transformation, a P/S 107 forconverting a parallel signal into a serial signal, a GI adding unit 108for adding a guard interval GI to a signal, an orthogonal modulator 109,and a transmission unit 110.

The modulator 102 maps the data 101 which are first data to betransmitted onto a complex plane to modulate sub-carriers. Based on data103 which are second input data, the pattern determination unit 104determines a pattern of particular signals associated with the data 103to be allocated to sub-carriers of a matrix formed by arranging aplurality of sub-carriers arranged in the direction of a frequency axisinto an array in the direction of a time axis to accommodate a pluralityof OFDM symbols. The particular signals may be sub-carriers which havebeen modulated according to a certain modulation method or null signalswhich involve no sub-carriers.

The mapping unit 105 allocates the pattern of the particular signalsdetermined by the pattern determination unit 104 to the matrix andallocates sub-carriers which have been modulated by the data 101 to theelements of the matrix other than the pattern of the particular signals.

The above-mentioned matrix will now be described with reference todrawings.

FIG. 2 shows the matrix formed by a plurality of sub-carriers arrangedin the direction of the frequency axis and a plurality of OFDM symbolsarranged in the direction of the time axis. FIG. 3 shows waveforms ofsub-carriers corresponding to the elements of the matrix formed by theplurality of sub-carriers arranged in the direction of the frequencyaxis and the plurality of OFDM symbols arranged in the direction of thetime axis. FIGS. 2 and 3 show an example in which the number ofsub-carriers in the direction of the frequency axis is 8, and the numberof OFDM symbols is 4.

In FIG. 2, D1 to D24 represent areas to which the sub-carriers modulatedby the data 101 are allocated, and S represents areas to which thepattern of the particular signals is allocated. The data 101 are thefirst data. The allocated positions and number of the areas S are variedon the basis of the data 103 input to the pattern determination unit104. The matrix as shown in FIG. 2 is stored as a data table in a memoryincorporated in the multi-carrier communication apparatus, and aconfiguration may be employed, in which the contents of the table (thenumber of sub-carriers and the number of OFDM symbols) can be freelychanged.

The IFFT 106 performs inverse Fourier transformation on the particularsignals and sub-carriers allocated to the matrix by the mapping unit 105to transform them into OFDM symbols in the direction of the time axisone at a time, and the signals in the direction of the frequency axisare thus transformed into signals in the direction of the time axis.

The P/S 107 converts the parallel signals in the direction of the timeaxis output by the IFFT 106 into serial signals in the direction of thetime axis. The GI adding unit 108 adds GIs to the signals output by theP/S 107 to suppress an interference of a delayed wave attributable tomultiple paths. The orthogonal modulator 109 performs orthogonalmodulation of a carrier wave using the signals added with GIs at the GIadding unit 108. The transmission unit 110 amplifies the power ofsignals output by the orthogonal modulator 109 and transmits the outputsignals into the air.

The multi-carrier communication apparatus according to this embodimentof the invention employs the orthogonal frequency division multiplexingin which all sub-carriers transmitted are in an orthogonal relationshipwith each other and in which adjoining sub-carriers are overlapped witheach other.

An operation of the multi-carrier communication apparatus shown in FIG.1 will now be described.

The multi-carrier communication apparatus sequentially performs primarymodulation of the data 101 which are the first data to be transmitted onthe basis of, for example, QPSK modulation (to thereby obtainsub-carriers which have been subjected to primary modulation using thedata 101). In the case of QPSK modulation, since the data are mapped to,for example, four symbols (1, 1), (−1, 1), (1, −1) and (−1, −1) on acomplex plane, two bits of data can be carried by (modulated into) onesymbol.

The multi-carrier communication apparatus determines a pattern ofparticular signals allocated to sub-carriers of the matrix based on thedata 103 which is second input data to be transmitted and allocates thesub-carriers modulated by the data 101 and the particular signals to thematrix according to the determined pattern.

The signals (the sub-carriers and the particular signals) allocated tothe matrix as described above are inverse- Fourier-transformed in thedirection of the time axis into one OFDM symbol at a time. They are thustransformed into serial signals and transmitted into the air on acarrier wave after GIs are inserted.

The amount of data which can be transmitted by the multi-carriercommunication apparatus shown in FIG. 1 will now be described withreference to FIGS. 2 and 3.

When the number of sub-carriers and the number of symbols are 8 and 4,respectively, as shown in FIGS. 2 and 3, the matrix formed will have 32elements. The number of combinations available for the allocation of,for example, eight particular signals to each of the elements of thematrix is ₃₂C₈=10518300. That is, the eight particular signals can beallocated to the matrix in 10518300 different patterns (>2^(23.3)), and23.3 bits of data can be transmitted as the second data.

Since the number of sub-carriers modulated by the data 101 and allocatedto the matrix is 32−8=24, the amount of data transmitted by thesub-carriers is 24×2 bits=48 bits. Therefore, the multi-carriercommunication apparatus shown in FIG. 1 can transmit 23.3 bits of datarepresented by the patterns of the particular signals and 48 bitsmodulated into 24 sub-carriers, i.e., 71.3 bits of data in total.

Here, it is compared the multi-carrier communication apparatus shown inFIG. 1 and the multi-carrier communication apparatus disclosed in PatentDocument 1. For example, the comparison will be made on an assumptionthat the number of sub-carriers is 8 that is the same as in theabove-described example; the number of sub-carriers selected is 6; andthe frequency band width and the number of OFDM symbols are the same asthose in the above-described example.

In this case, the multi-carrier communication apparatus disclosed inPatent Document 1 can transmit ₈C₆ patterns (which substantially equal4.8 bits) of data determined by the number of combinations for selectionof six from among the eight sub-carriers and data allocated to each ofthe six sub-carriers selected or 2 bits×6=12 bits of data. That is, 16.8bits of data can be transmitted in total with one OFDM symbol.Therefore, the amount of data that the multi-carrier communicationapparatus disclosed in Patent Document 1 can transmit with four OFDMsymbols is 16.8 bits×4=67.2 bits.

It will be understood from above that the amount of data which can betransmitted by the multi-carrier communication apparatus in the thisembodiment of the invention is greater than that of the related art by4.1 bits (17 times or more in terms of data volume) or more. The amountof data that can be transmitted by the multi-carrier communicationapparatus shown in FIG. 1 is greater, by 7.3 bits (157 times in terms ofdata volume) or more, than the amount of data (2 bits×32=64 bits) whichcan be transmitted using a general multi-carrier transmission system inwhich data are allocated to each of the six sub-carriers only.

As described above, in the embodiment of the invention, patterns ofparticular signals determined in association with the data 103 areallocated to a matrix having a plurality of columns and rows formed by aplurality of sub-carriers arranged in the direction of a frequency axisand a plurality of symbols arranged in the direction of a time axis toallow data to be transmitted in a number of bits which depends on thenumber of combinations of the patterns. The number of patterns of theparticular signals greatly increases the greater the size of the matrixbecomes, and this allows a great increase in the amount of second data103 that can be transmitted. Thus, a much greater amount of data can betransmitted compared to the related art.

In the embodiment of the invention, since 71.3 bits of data can betransmitted with four OFDM symbols as described in the above example,the amount of data that can be transmitted per unit time (one OFDMsymbol) is 17.8 bits. The amount of data transmitted per unit time by amulti-carrier communication apparatus according to the related art is 16bits or 16.8 bits under the same conditions, which indicates that theamount of data transmitted per unit time can be increased by nearly 1bit and that data can therefore be transmitted more efficiently.

In the embodiment of the invention, the numbers of sub-carriers in thedirection of the frequency axis and OFDM symbols in the direction of thetime axis forming the matrix and the number of the particular signalsare not limited to those in the above-described example, and they may bearbitrarily set within respective allowable ranges.

The method of modulation used in the modulator 102 in the embodiment ofthe invention is not limited to the QPSK method (2 bits/symbol), and anymodulation method such as BPSK (1 bit/symbol), 8PSK (3 bits/symbol),16QAM (4 bits/symbol) or 64QAM (6 bits/symbol) may be chosen as long asthe modulation methods allows data to be mapped onto a complex plane.

Advantages similar to those described above can be achieved when primarymodulation is followed by spread spectrum multiplexing as in the case ofmulti-carrier DS-CDMA (MC/DS-CDMA) in which primary modulation by themodulator 102 in the embodiment of the invention is directly followed byspread spectrum multiplexing to perform orthogonal frequency divisionmultiplexing.

When sub-carriers which have been subjected to a particular modulationmethod are used as the particular signals, it is only required that themodulation method can be distinguished from the modulation method usedin the modulator 102, and any method of modulation may be employed aslong as such a requirement is satisfied.

SECOND EMBODIMENT

A multi-carrier communication apparatus for explaining a secondembodiment of the invention serves as a receiver for receiving signalstransmitted by the multi-carrier communication apparatus descried in thefirst embodiment of the invention.

FIG. 4 shows a schematic configuration of the multi-carriercommunication apparatus for explaining the second embodiment of theinvention.

In the same figure, the multi-carrier communication apparatus includes areception unit 201 for receiving signals from the outside, an orthogonaldemodulator 202, a GI removing unit 203 for removing GIs from thesignals, a S/P converter 204 for converting serial signals into parallelsignals, an FFT 205 which performs Fourier transformation, a patterndetection unit 206 for detecting patterns of particular signals, ademapping unit 207, a demodulator 208, and another demodulator 210.

The orthogonal demodulator 202 converts signals received by thereception unit 201 into in-phases component I and orthogonal componentsQ. The GI removing unit 203 establishes synchronization between OFDMsymbols and removes the guard intervals GI from signals output by theorthogonal demodulator 202. The S/P converter 204 converts signals inthe direction of a time axis from which guard intervals GI have beenremoved into parallel signals. The FFT 205 performs Fouriertransformation of the parallel signals in the direction of the time axisoutput by the S/P converter 204 to transform them into a plurality ofsub-carriers arranged in the direction of a frequency axis.

The pattern detection unit 206 detects a pattern of particular signalsallocated to sub-carriers in the form of a matrix formed by arranging aplurality of sub-carriers arranged in the direction of the frequencyaxis output by the FFT 205 into a plurality of symbols arranged in thedirection of the time axis in the order in which the sub-carriers arereceived.

The demapping unit 207 removes the particular signals allocated to thematrix based on the pattern of the particular signals detected by thepattern detection unit 206 and rearranges each of the sub-carriers whichhave been allocated to the remaining part of the matrix and which havebeen modulated by first transmitted data in the order in which thesub-carriers are to be demodulated.

The demodulator 208 demodulates the sub-carriers which have beenrearranged by the demapping unit 207 to obtain first received data (data209) which are identical to the first transmitted data. The demodulator210 restores second received data (data 211) which are identical tosecond transmitted data associated with the pattern of the particularsignals detected by the pattern detection unit 206.

The multi-carrier communication apparatus in the embodiment of theinvention employs orthogonal frequency division multiplexing in whichall sub-carriers received are in an orthogonal relationship with eachother and in which adjoining sub-carriers are overlapped with eachother.

An operation of the multi-carrier communication apparatus shown in FIG.4 will now be described.

Signals received from the multi-carrier communication apparatus shown inFIG. 1 are converted into signals having in-phase components I andorthogonal components Q, and guard intervals GI are removed from thesignals after synchronization of OFDM symbols is established. Thesignals from which guard intervals GI have been removed are convertedinto parallel signals which are subjected to Fourier transformation tobe transformed into signals in the direction of the frequency axis.

Thereafter, the pattern of the particular signals allocated tosub-carriers in a matrix (see FIG. 2) formed by arranging a plurality ofsub-carriers arranged in the direction of the frequency axis that arethe Fourier-transformed signals into an array of a plurality of symbolsin the direction of the time axis in the order in which the sub-carriershave been received.

When the pattern of the particular signals is detected, the particularsignals are removed from the matrix based on the pattern, and thesub-carriers left on the matrix are rearranged in the order in whichthey are to be demodulated. Thus, the first transmitted data (firstreceived data) are demodulated, and the second transmitted data (secondreceived data) associated with the pattern of the particular signals arerestored.

As described above, in the embodiment of the invention, signalstransmitted by the multi-carrier communication apparatus described inthe first embodiment of the invention are received; the pattern ofparticular signals associated with data 103 is detected from a matrix asshown in FIG. 2 formed based on the signals; and second received datacan be obtained by restoring the data 103 associated with the pattern ofthe particular signals thus detected. As thus described, themulti-carrier communication apparatus described in the embodiment of theinvention receives data transmitted by the multi-carrier communicationapparatus shown in FIG. 1 and can obtain first transmitted data andsecond transmitted data from the data. It is therefore possible toincrease the amount of data that can be received dramatically.

Any modulation method such as BPSK (1 bit/symbol), 8PSK (3 bits/symbol),16QAM (4 bits/symbol) or 64QAM (6 bits/symbol) may be chosen themodulation method used in the demodulator 208 in the embodiment of theinvention.

When a communication system is configured using the multi-carriercommunication apparatus shown in FIGS. 1 and 2 and described above, thecommunication system will be able to perform data communication withhigh efficiency.

While the invention has been described in detail with reference toparticular embodiments for carrying out the same, it will be apparent tothose skilled in the art that various modifications and alterations maybe made to the invention without departing the sprit and scope of thesame.

The present application is based on Japanese patent application No.2003-118767 filed on Apr. 23, 2002, and the contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

The invention makes it possible to provide a multi-carrier communicationapparatus capable for greatly increasing the amount of data per unittime with the frequency band width unchanged.

1. A multi-carrier communication apparatus for transmitting data using aplurality of sub-carriers, comprising: a determining unit whichdetermines a pattern of particular signals associated with first data;an allocating unit which allocates the determined pattern tosub-carriers of a matrix, the matrix is formed by arranging a pluralityof sub-carriers arranged in a direction of a frequency axis in adirection of a time axis; an allocating unit which allocatessub-carriers modulated by second data to a part of the matrix other thanthe particular signals; and a transmitting unit which transmits theparticular signals allocated to the matrix and the sub-carriersmodulated by the second data.
 2. A multi-carrier communicationapparatus, comprising: a detecting unit which detects a pattern ofparticular signals associated with first data which are allocated tosub-carriers of a matrix formed by arranging a plurality of sub-carriersarranged in a direction of a frequency axis obtained from received datain a direction of a time axis; a restoring unit which restores the firstdata associated with the detected pattern; and a demodulating unit whichdemodulates second data from sub-carriers which are modulated by thesecond data allocated to a part of the matrix other than the particularsignals.
 3. The multi-carrier communication apparatus as set forth inclaim 1 or 2, wherein each of the plurality of sub-carriers arranged inthe direction of the frequency axis has an orthogonal relationship witha sub-carrier adjacent thereto.